A while ago while at Touro LA, some classmates and I took a class where we researched information and then discussed some ways to help Jewish youth.
The situations we studied were for example,
One situation is where the home environment might Not be enjoyable. They just feel the strictness of do's and don'ts, but they don't see the beauty in their heritage, and they look for something different. To improve this, we need to add some warmth and joy to the environment, so they want to continue it when on their own.
There's also those that feel intellectually frustrated if their questions are not answered. For this, we should take the time to talk to them and find information to help them strengthen their knowledge and emunah
Another scenario is when some individuals go to college and find out things that go against what they learned. If they don't have a strong foundation, this can hurt them. One of my classmates suggested that before this person goes to college, they should be told beforehand what they might encounter, for example, "They believe in evolution where.....but we don't because....."
There are also teens that get turned off when they see a bad example of someone who should know better, and yet acts poorly. Obviously, we all make mistakes, but it still gives them a negative impression, which is why we need to be careful with middos and behavior.
Something that a friend mentioned to me recently is that Some students have a hard time keeping up with the learning. For example, they might not be ready to learn Gemorah yet, and need some time learning something else before that. And so they should given something that's more on their level so they can thrive.
Well I hope this message helps. Of course, there are plenty of other scenarios that also occur. I know that this message is easier said than done. It takes time, effort, patience and prayer. May Hashem help our good efforts succeed in making a good impact